Ensure lsan is initialized (#20790)

This fixes lsan.test_pthread_exit_main_stub.

I think this a bug upstream bug hasn't been noticed because it only
shows up in some rare circumstances.

- no dynamic memory allocation function is called (e.g. malloc/free)
- pthread_create is not called
- pthread_exit (or some other pthread API) *is* called
- SANITIZER_CAN_USE_PREINIT_ARRAY is not defined

Author: sbc100

.circleci/config.yml

@@ -523,7 +523,8 @@ jobs:
             asan.test_asyncify_longjmp
             lsan.test_stdio_locking
             lsan.test_dlfcn_basic
-            lsan.test_pthread_create"
+            lsan.test_pthread_create
+            lsan.test_pthread_exit_main_stub"
       - freeze-cache
       - run-tests:
           # also run a single test of EMTEST_BROWSER=node.

system/lib/compiler-rt/lib/lsan/lsan_thread.cpp

@@ -45,7 +45,10 @@ void InitializeThreads() {
   thread_arg_retval = new (thread_arg_retval_placeholder) ThreadArgRetval();
 }
 
-ThreadArgRetval &GetThreadArgRetval() { return *thread_arg_retval; }
+ThreadArgRetval &GetThreadArgRetval() {
+  ENSURE_LSAN_INITED;
+  return *thread_arg_retval;
+}
 
 ThreadContextLsanBase::ThreadContextLsanBase(int tid)
     : ThreadContextBase(tid) {}